JPH08307714A - Device and method for color conversion - Google Patents

Abstract

PURPOSE: To stabilize color reproducibility by executing correction with high accuracy by constitution of simplicity and light weight when color reproducing characteristic is fluctuated. CONSTITUTION: This color converter which executes color correction based on a memory map system by using lattice point data stored in advance is equipped with an image processing part 100 which converts data for correction color-corrected based on the memory map system by a (γ) table and outputs it finally, a color measuring instrument 107 which measures the color reproducing characteristic of an image outputted by the image processing part 100, and a correction part 106 which predicts an output value based on the memory map system and interpolates the table so as to keep difference between such predictor and the predictor of the color measuring instrument 107 at a value less than the one decided in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a full-color printer or a full-color digital copying machine for color-correcting input image data and then forming a reproduced color image, and an image display apparatus such as a color CRT or a color liquid crystal display. The present invention relates to a color conversion device and a color conversion method for absorbing a temporal change by adding a calibration function of the color reproduction characteristic even when the color reproduction characteristic changes with time.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using a memory map is known as an image forming apparatus for performing color correction of a color image signal. For example, the following two documents are known as reference technical documents for constructing this memory map and performing color correction using the memory map. First, Japanese Examined Japanese Patent Sho5
8-16180, "Signal Interpolation Method in Memory Device", and Secondly, Japanese Patent Laid-Open No. 5-75
There is an "interpolation method and color correction method" disclosed in Japanese Patent No. 848.

In these color correction methods, gamut (color reproduction area) is divided into tetrahedron (Japanese Patent Publication No. 58-16180) or triangular prism (Japanese Patent Laid-Open No. 5-75848) (hereinafter, referred to as
(Divided space), its vertices (hereinafter referred to as grid points) are made to correspond to color interpolation data, and stored in a memory in advance. For input, it is judged which divided space the data belongs to, and the corresponding The grid point data of the divided space is read from the memory, and the color correction value is calculated by linear interpolation from the positional relationship between the grid point data and the input with respect to the divided space.

However, in a full-color image device using the above-mentioned color correction method, there is a problem that the color reproduction characteristics in the initial stage vary depending on the use conditions and the passage of time, and a good reproduced image cannot be maintained for a long period of time. there were. In particular, a digital color copying machine using an electrophotographic process is known as a typical image forming apparatus, but toner replenishment is required in addition to characteristic changes due to use deterioration of parts and use environment conditions such as temperature and humidity. It was difficult to maintain document reproducibility with high accuracy due to the addition of characteristic changes caused by repeated output. Further, in a CRT, which is a typical example of image display devices, reproduction color variation has occurred due to deterioration of the tube surface light emitter and variation of the electron beam generating cathode applied voltage. Therefore, conventionally, a so-called calibration function has been provided to restore the changed amount to the initial level.

[0005] For example, the following two are known to deal with the above-mentioned variation of reproduced color over time. First
And a "digital color copying machine" disclosed in Japanese Patent Laid-Open No. 3-84563. In this method, a color chart is created by a recording apparatus, the color chart is read by an original reading apparatus, and the parameter or conversion procedure for color data conversion is changed based on the color chart. Secondly, JP-A-63-18446
This is the "color color conversion device" disclosed in Japanese Patent Publication No. This is to set the color conversion coefficient so that the output of the color conversion means has a predetermined value corresponding to a standard color original.

[0006]

However, in the conventional technique as described above, since the reading characteristic of the original reading device for reading the color chart is changed, a highly accurate calibration result cannot be obtained. In addition, in the case of a single printer or the like, there is a problem that a document reading device must be separately prepared, which hinders reduction in size and weight and cannot perform high-speed calibration processing.

Further, if the calibration level (accuracy) is fixed as in the conventional case, for example, when color fidelity is not so demanded, high precision calibration is not required, but the determined calibration is performed. Since processing is performed, there is a problem that the waiting time until the actual output takes a long time.

Further, when the calibration process is executed, the calibration information previously executed, for example, the date and time and the calibration data used for the calibration are unknown, so that the interval for performing the calibration process can be clearly understood. There is a problem that it is not efficient because it is not possible or the process of obtaining the optimum calibration data has to be redone from the beginning.

In addition, even if the color reproduction characteristic of the apparatus is slightly changed, the user may not notice it, and there is a problem that it is not possible to grasp an accurate calibration timing for maintaining highly accurate color reproduction. there were.

The present invention has been made in view of the above, and when the color reproduction characteristics are changed, a simple and small-sized configuration can be used to perform high-accuracy calibration at high speed. The first purpose is to stabilize the reproduction characteristics.

A second object is to make it possible to adjust the color reproducibility and improve the processing efficiency in accordance with the required quality level when the calibration is required.

A third object of the present invention is to make it possible to refer to the calibration history and the calibration data used at that time so that the necessity of calibration and the calibration process can be easily executed.

A fourth object is to monitor the variation of the color reproduction characteristic that the user does not notice and to be able to execute the calibration processing for obtaining a highly accurate reproduction quality at an appropriate timing.

[0014]

In order to achieve the above object, in a color conversion apparatus according to a first aspect of the present invention, color correction based on a memory map method is used by using previously stored grid point data. In a color conversion device to be executed, image processing means for converting calibration data color-corrected based on the memory map method by a γ table and finally outputting, and color reproduction characteristics of an image output by the image output means are measured. Calibration means for predicting an output value based on the memory map method, and interpolating the γ table so that the difference between the predicted value and the measured value of the measuring means is less than a predetermined value. And means.

According to a second aspect of the present invention, there is provided a color conversion method, wherein color correction based on a memory map method is executed using grid point data stored in advance. A first step of predicting an output value by the method, a second step in which the calibration data is color-corrected based on the memory map method and then actually output, and the output image is measured; and a second step in which the measurement is performed. A third step of calculating the sum of the differences between the measured value and the predicted value of the first step, varying the γ table corresponding to each color so that the total becomes less than or equal to a predetermined value, and calibrating the γ table. And the steps of.

Further, in the color conversion method according to the third aspect, the color conversion method for executing the color correction based on the memory map method using the grid point data in which the color correction based on the memory map method is stored in advance. In, a first step of setting a reference value for ending the calibration process, a second step of predicting an output value based on the memory map method, and color correction data for calibration data based on the memory map method. After that, a third step of actually outputting and measuring the output image, and a sum total of the differences between the measurement values measured by the third step and the predicted values of the second step are calculated, and the sum is calculated as described above. The fourth step of calibrating the γ table by changing the γ table corresponding to each color so that the γ table becomes equal to or less than the reference value set in the first step.

Further, in the color conversion apparatus according to the fourth aspect, the calibration processing is executed in the color conversion apparatus that executes the color correction based on the memory map method using the grid point data stored in advance. Timing means for timing the date and time, calibration data storage means for storing the date and time clocked by the timing means and its calibration data, and calibration for executing calibration processing based on the calibration information stored in the calibration data storage means And means.

Further, in the color conversion device according to the fifth aspect, in the color conversion device which executes the color correction based on the memory map method using the grid point data stored in advance, it contributes to the color reproduction characteristic. Monitoring means for monitoring the fluctuation state of the part, calibration notifying means for judging the necessity of calibration based on the monitoring information obtained by the monitoring means, and notifying accordingly, and notification information sent from the calibration notifying means. And display means for displaying.

[0019]

According to the color conversion device (claim 1) of the present invention, the calibration data color-corrected based on the memory map method is converted into γ
The table is converted, the final output is made, and the color reproduction characteristics of the image are measured. In addition, the output value is predicted based on the memory map method, and the γ table is interpolated so that the difference between the predicted value and the above measured value is less than or equal to the predetermined value. Enables highly accurate calibration.

In the color conversion method (claim 2) according to the present invention, first, the output value is predicted based on the memory map method. After that, the calibration data is color-corrected based on the memory map method and then actually output, the output image is measured, the sum of the differences between the measured value and the predicted output value is calculated, and the sum is predetermined. The γ table corresponding to each color is changed so as to be equal to or less than the value, and the γ table for calibration of each color is interpolated and created, thereby creating a table that absorbs changes over time.

Further, in the color conversion method according to the present invention (claim 3), a predetermined value of the color difference in the calibration processing is set, the output value is predicted based on the memory map method, and the calibration data is converted into the memory map method. After the color correction based on the actual output, the output image is measured, the total sum of the difference between the measured value and the predicted output value is calculated, and the γ table corresponding to each color is set so that the total becomes less than or equal to the predetermined value. By changing the value of γ and interpolating the γ table for calibration of each color to create a calibration table according to the set predetermined value, that is, a calibration table according to the required calibration level.

The color conversion device according to the present invention (claim 4) stores calibration information such as the date and time of previous calibration and its calibration data, and executes the calibration from the date and time of calibration. By determining the necessity and referring to the calibration data stored at the time of calibration, the efficiency of the calibration process is improved.

Further, the color conversion device according to the present invention (claim 5) monitors the fluctuation of the factor affecting the color reproduction characteristic and notifies the user of the necessity of calibration based on the monitoring result. Then, accurately grasp the fluctuations that you do not notice, and execute the calibration at an appropriate timing.

[0024]

【Example】

(Structure of Embodiment 1) An embodiment of a color conversion device according to the present invention will be described below with reference to the accompanying drawings. In this embodiment, a color conversion device (see FIG. 1) corresponding to an image forming device (hereinafter, referred to as a printer) that forms a color image with three colors of Y, M, and C, and Y, M, C, and K. A color conversion device (see FIG. 2) compatible with a printer that forms a color image with four colors will be described. Further, the color signals in FIGS. 1 and 2 can be made compatible with an image display device (hereinafter referred to as a display) by replacing the YMC of the printing system with RGB and ymc with rgb.

FIG. 1 is a block diagram showing the main configuration of a color conversion device in a three-color printer according to this embodiment. In the figure, an image processing unit 100 as an image processing means has functional blocks 101 to 105 described below. It is composed by. That is, 101 is an input digital Y, M,
A γ table for γ-converting the C input signal and outputting y, m, and c signals, and 102 is a front part for outputting each of the signals from the γ table 101 as divided spatial data S ₁ , S ₂ , and S ₃ for color correction. A conversion unit 103 is a color correction unit that performs color correction by an interpolation method using a memory map and outputs y ′, m ′, c ′.
Reference numeral 04 represents the correction data from the color correction unit 103 in y ″, m ″,
A post-conversion unit 105 for converting into digital data of c ″ is a γ table for γ-converting each color data from the post-conversion unit 104 and outputting final outputs Y ′, M ′, C ′.

Reference numeral 106 is a calibrating unit as a calibrating unit that uses the grid point data for calibration and generates calibration data based on the memory map method, and 107 is the γ table 105.
It is a color measuring device as a measuring device having a simple structure that can actually measure the color of Y ′, M ′, and C ′ output via the color measuring device.

FIG. 2 is a block diagram showing the main construction of the color conversion device in the four-color printer according to this embodiment. Image processing for processing four colors by adding K (black) color to that in FIG. It constitutes part 200. That is, since the function is the same as that of FIG. 1, the same reference numeral as that of FIG. However, the pre-conversion unit 102 uses the UCR
/ Has a UCA processing function.

(Operation of Embodiment 1) Next, the operation of the color conversion device configured as described above will be described. Y, M,
Digital color signals of three colors of C or four colors of Y, M, C and K are input to the γ table 101. Each color signal has a value of 256 levels of 0 to 256 gradations in 8 bits. In the following, description will be made by taking three color signals of Y, M and C as an example. The input signal is γ converted by the γ table 101 and input to the pre-conversion unit 102 as y, m, c. The pre-transformation unit 102 outputs divided space data S ₁ , S ₂ , S ₃ corresponding to y, m, c. That is,
In order to execute the correction based on the memory map interpolation, the divided space data S ₁ and S for selecting the grid points for interpolation
₂ and S ₃ are generated.

Subsequently, the color correction unit 103 interpolates the input color space by the memory map using the divided space data S ₁ , S ₂ , S ₃ and outputs y ', m', c '.
Next, the respective signals of y ′, m ′, and c ′ are converted into y ″, m ″, and c ″ by the post-conversion unit 104, and further, γ
It is converted through the table 105 as digital signals Y ', M', C'as the final output. That is, the ink (or toner) control amounts Y ′, M ′, C ′ corresponding to the three-color printer are output.

By the way, since the above Y ', M'and C'may fluctuate due to use conditions and temporal factors, in the present embodiment, the calibration section 106 and the color measuring instrument 107 are provided.
A calibration function is added to support this. The processing operation of this portion will be described below with reference to the flowchart shown in FIG. In the figure, when this process is started, first, the calibration unit 106 outputs an output predicted value (S30
1), N pieces of calibration data are loaded (S302), and this is output as an image (S303). Therefore, the color measuring device 107
Then, the output image is actually measured (S304).

Next, a total sum ΣΔ of N differences between the measured values and the predicted output values o, p, q of the calibration unit 106 is obtained (S30).
5), it is determined whether or not this ΣΔ is greater than or equal to a predetermined value Th. That is, the judgment of Th ≦ ΣΔ is executed (S306). If it is determined that Th ≦ ΣΔ does not hold, the γ table 105 for each color is changed (S
307), a new ΣΔ is calculated (S308), the process returns to step S306, and the same process is repeatedly executed. On the other hand, in step S306, Th ≦ ΣΔ
If it is determined that, the γ table 105 for each color is interpolated (S309), and this processing operation is ended. In this way, the calibration unit 106 can predict the data that will be output without performing actual image output, by performing the calibration output once.

Further, the above operation will be described in detail. Like the color correction unit 103, the calibration unit 106 includes calibration grid point data, and executes interpolation by a memory map for color correction using the grid point data. That is,
The predicted output value opq is output based on the three-dimensional input. This predicted output value opq predicts the same type of data so as to take the difference from the actually measured data. For example, when the measured value is the tristimulus value XYZ, L * a * b *, L * u * v *, and YIQ correspond to opq = XYZ.

If the difference between the two data is Δ, then L
* A * b * and L * u * v * are given by the following equations. ΔE ^* _ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* )
² ] ^1/2 ΔE ^* _uv = [(ΔL ^* ) ² + (Δu ^* ) ² + (Δv ^* )
² ] ^1/2 Also, since it is the difference in other XYZ, YIQ, etc., it can be calculated in the same manner by the three-dimensional Euclidean distance. The above process is used only at the time of calibration.

Further, as described above, N pieces of calibration data prepared in advance are loaded from a calibration memory (not shown), and a total sum ΣΔ of N pieces of the difference is obtained, and ΣΔ is the minimum. The γ table 105 is changed for each color so that Therefore, the calibration process is terminated when the value is less than or equal to the predetermined value Th. At the end time, since the γ table 105 for each color has only a small amount of data in 256, interpolation processing is performed based on the calibration value obtained above, and a 256 level table is created. Therefore, the calibrated γ-table 10 considering the change with time is used.
By passing each color signal through 5, it is possible to obtain an output in which the change with time is absorbed, that is, a stable image output.

By the way, although the calibration in the above color conversion has been described as for the printer, when it is used as the calibration for the display such as CRT, the light source color displayed on the device can be measured instead of the color measuring device 107. It suffices to prepare a measuring instrument and execute the same calibration process as above from the difference from the data measured by this measuring instrument.

(Effect of First Embodiment) According to the first embodiment, a simple measuring device is added to a full-color image device that is originally not equipped with the image data reading function, and the actual output of the device is reduced to 1. Measures only once, then predicts the output value using the memory map method, and creates a table that absorbs variations in color reproduction characteristics from the predicted value, so a simple and lightweight configuration realizes high-speed calibration processing. can do.

[Embodiment 2] This embodiment shows an example in which the calibration end value Th in Embodiment 1 can be arbitrarily set.

(Operation of Second Embodiment) The operation of the second embodiment will be described using the color conversion device having the same configuration as that of the first embodiment.
FIG. 4 is a flow chart showing the calibration processing operation according to the second embodiment, which is the same as the operation of FIG. This will be described below with reference to FIG. First, the calibration unit 106 outputs the predicted output value (S401), and the calibration end reference value T is output.
Directly input h as a desired value (S402). In this case, prior knowledge about color difference is required. When the input of Th is completed, then, similarly to FIG. 3,
N pieces of calibration data are loaded (S403), and this is output as an image (S404). Therefore, the output image is actually measured by the color measuring device 107 (S405).

Next, a total sum ΣΔ of N differences between the measured values and the predicted output values o, p, q of the calibration unit 106 is obtained (S40).
6) It is determined whether or not this ΣΔ is equal to or larger than a predetermined value Th. That is, the judgment of Th ≦ ΣΔ is executed (S407). If it is determined that Th ≦ ΣΔ does not hold, the γ table 105 for each color is changed (S
408), a new ΣΔ is calculated (S409), the process returns to step S407, and the same process is repeated. On the other hand, in step S407, Th ≦ ΣΔ
If it is determined that, the γ table 105 for each color is interpolated (S410), and this processing operation is ended.

(Effect of Embodiment 2) According to Embodiment 2, since the reference value Th at the end of calibration can be set arbitrarily, fidelity of reproduced color is not so high even when calibration is required. If you don't care, you can reduce the processing time until output because you don't perform highly accurate calibration calculations. Further, the color reproducibility can be adjusted according to the required image quality.

[Embodiment 3] In the present embodiment, the value Th at the end of calibration in the above-mentioned Embodiment 1 is divided into levels in advance, and T is obtained.
It shows an example in which a desired one can be selected from h.

(Operation of Third Embodiment) The operation of the third embodiment will be described using the color conversion device having the same configuration as that of the first embodiment.
FIG. 5 is a flow chart showing the calibration processing operation according to the third embodiment, and an operation of selecting the calibration end value Th is added to the operation of FIG. 3 described in the first embodiment.
This will be described below with reference to FIG. First, the calibration unit 106 outputs the predicted output value (S501), and displays the calibration completion value Th divided into levels (S502). For example, this level division is set as follows so that it can be selected without prior knowledge about color difference. That is, Level 1: General calibration Level 2: Professional, 10 for Th level 1, 5 for Th
And so on. In this case, as the level becomes higher, the calibration time is naturally required.
However, since the device has its own calibratable capacity Th _min , if a value below this is set, it is forcibly set to Th _min .

When the Th level is displayed in step S502, the Th level is selected from the display screen (S503), and it is determined whether or not the desired Th level is selected (S504). If it is determined that the desired Th level has been selected, N pieces of calibration data are loaded (S505) and output as an image (S506), as in the first embodiment. Therefore, the output image is actually measured by the color measuring device 107 (S507).

Next, a total sum ΣΔ of N differences between the measured values and the predicted output values o, p, q of the calibration unit 106 is obtained (S50).
8) Then, it is determined whether or not this ΣΔ is greater than or equal to a predetermined value Th. That is, the judgment of Th ≦ ΣΔ is executed (S509). If it is determined that Th ≦ ΣΔ does not hold, the γ table 105 for each color is changed (S
510), a new ΣΔ is calculated (S511), the process returns to step S509, and the same process is repeatedly executed. On the other hand, in step S509, Th ≦ ΣΔ
If it is determined that, the γ table 105 for each color is interpolated (S512), and this processing operation is ended.

(Effect of Embodiment 3) Therefore, as described above, since the reference value Th at the end of the calibration is divided into two levels, for example, the general calibration and the professional calibration, which can be selected, Similarly, even when calibration is required, when the fidelity of the reproduced color is not so important, it is possible to shorten the processing time until output because high-precision calibration calculation is not performed. Further, the color reproducibility can be adjusted according to the required image quality.

[Embodiment 4] In the present embodiment, the history of the execution of the above-mentioned calibration processing is stored, the calibration information is displayed, and the calibration processing can be executed with the optimum calibration data previously performed. It is a thing.

(Structure of Embodiment 4) This embodiment has the function shown in FIG. 6 in addition to the structure shown in FIG. 1 or 2. FIG. 6 is a block diagram showing a system configuration according to the fourth embodiment. In the figure, 601 is an image forming apparatus (printer).
Alternatively, any one of image display devices (display), 602 is a timer having a timer function for holding calibration date and time, and 603 is a calibration memory for storing data used for calibration.

(Operation of the Fourth Embodiment) FIG. 7 is a flowchart showing the calibration processing operation according to the fourth embodiment.
The operation of retaining the calibration data and reusing it is added to the operation of FIG. This will be described below with reference to FIG. First, the calibration unit 106 outputs the predicted output value (S701) and loads N calibration data (S7).
02), and outputs this as an image (S703). Therefore, the output image is actually measured by the color measuring device 107 (S704).

Next, a total sum ΣΔ of N differences between the measured values and the predicted output values o, p, q of the calibration unit 106 is obtained (S70).
5), it is determined whether or not this ΣΔ is greater than or equal to a predetermined value Th. That is, the judgment of Th ≦ ΣΔ is executed (S706). If it is determined that Th ≦ ΣΔ does not hold, the γ table 105 for each color is changed (S
707), a new ΣΔ is calculated (S708), the process returns to step S706, and the same processing is repeatedly executed. On the other hand, in step S706, Th ≦ ΣΔ
If it is determined that, the γ table 105 for each color is interpolated (S709).

Subsequently, it is determined whether or not to save the above calibration data (S710). If it is determined that the calibration data is to be saved, a time stamp for specifying the date and time of the calibration data is added, the calibration data is saved (S711), and this processing is ended.

(Effect of Embodiment 4) According to Embodiment 4, since the date and time when the calibration is performed can be confirmed, the user can judge in advance whether or not the calibration period is necessary from the date and time data.

[Embodiment 5] In this embodiment, the state of the apparatus is monitored, and when a factor requiring calibration occurs,
This is a notification to that effect.

(Structure of Fifth Embodiment) FIG. 8 is a block diagram showing the structure of a monitoring apparatus according to the fifth embodiment. In FIG. 8, reference numerals 801 to 803 denote parts that affect the color reproduction characteristics. The fluctuation factor units A to C and 804 to 806 are connected to the fluctuation factor units A to C, respectively, and the sensors A to C and 807 as the monitoring means for monitoring the fluctuation state are the sensors A to C.
A calibration notification generation unit as a calibration notification means for inputting the monitoring result of C and notifying the necessity of calibration, 808 is a calibration notification generation unit 8
The display unit is a display unit that displays the notification information 07.

(Operation of Embodiment 5) Next, the operation of the above configuration will be described. The parts that change the color reproduction characteristics due to changes over time in the device or changes in operating conditions such as environmental conditions, that is, the states of the fluctuation factors A to C are monitored by the respective sensors A to C, and the monitoring results are notified of calibration. It is given to the generation unit 807. The calibration notification generation unit 807 collectively manages the monitoring information of the sensors A to C, and when the condition to be calibrated is reached, the calibration notification generation unit 807 provides the display unit 808 with notification information requiring calibration. Then, the display information is displayed on the display unit 808 to notify the user that calibration is required.

(Effect of Embodiment 5) According to Embodiment 5, a sensor for monitoring the fluctuation state is provided in the functional portion that contributes to the color reproduction characteristic, and the user knows and notifies the device fluctuation. ， Calibration process can be executed at appropriate timing.

[0056]

As described above, according to the color conversion device (claim 1) of the present invention, the calibration data color-corrected based on the memory map method is converted by the γ table and finally output. ， Measure the color reproduction characteristics of the image. In addition, the output value is predicted based on the memory map method, and the γ table is interpolated so that the difference between the predicted value and the measured value is equal to or less than the predetermined value.
High-accuracy calibration can be performed at high speed, and color reproduction characteristics can be stabilized.

According to the color conversion method (claim 2) of the present invention, first, the output value is predicted based on the memory map method. After that, the calibration data is color-corrected based on the memory map method and then actually output, the output image is measured, the sum of the differences between the measured value and the predicted output value is calculated, and the sum is predetermined. By changing the γ table corresponding to each color so that it becomes less than or equal to the value and interpolating the γ table for calibration of each color, a table that absorbs changes over time is created, so high-accuracy calibration can be performed at high speed. It is possible to stabilize the color reproduction characteristics.

According to the color conversion method of the present invention (claim 3), the predetermined value of the color difference in the calibration process is set, the output value is predicted based on the memory map method, and the calibration data is stored in the memory map. After color correction based on the method, actual output is performed, the output image is measured, the total sum of the differences between the measured value and the output predicted value is calculated, and each color is handled so that the total becomes equal to or less than the predetermined value. By changing the γ table and interpolating the γ table for calibration of each color,
Calibration according to the set predetermined value, that is, a calibration table according to the required calibration level is created. Therefore, when the calibration is necessary, the color reproducibility corresponding to the required quality level can be adjusted, and the processing efficiency can be improved.

According to the color conversion device of the present invention (claim 4), calibration information such as the date and time of previous calibration and the calibration data thereof is stored, and the calibration is performed from the date and time of calibration. It is possible to improve the efficiency of the calibration process by determining whether or not to execute the above and referring to the calibration data stored at the time of calibration. Therefore, the calibration history and the calibration data used at that time can be referred to, and the necessity of calibration and the calibration process can be easily performed.

Further, according to the color conversion apparatus (Claim 5) of the present invention, the fluctuation of the factor affecting the color reproduction characteristic is monitored, and the necessity of calibration is notified based on the monitoring result. In addition, it is possible to monitor variations in color reproduction characteristics that the user does not notice and to perform calibration processing at a proper timing in order to stably obtain highly accurate reproduction quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing the main configuration of a color conversion device in a three-color printer according to this embodiment.

FIG. 2 is a block diagram showing the main configuration of a color conversion device in a four-color printer according to this embodiment.

FIG. 3 is a flowchart showing a calibration processing operation according to the first embodiment.

FIG. 4 is a flowchart showing a calibration processing operation according to the second embodiment.

FIG. 5 is a flowchart showing a calibration processing operation according to the third embodiment.

FIG. 6 is a block diagram showing a system configuration according to a fourth embodiment.

FIG. 7 is a flowchart showing a calibration processing operation according to the fourth embodiment.

FIG. 8 is a block diagram illustrating a configuration of a monitoring device according to a fifth embodiment.

[Explanation of symbols]

101 γ table 103 color correction unit 105 γ table 106 calibration unit 107 color measuring instrument 602 timer 603 calibration memory 801 to 803 variation factor unit 804 to 806 sensor 807 calibration notification generation unit 808 display unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Manabu Komatsu 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Etsuro Morimoto 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Company Ricoh

Claims (5)

[Claims] 1. A color conversion device that executes color correction based on a memory map method using grid point data stored in advance, and converts calibration data color-corrected based on the memory map method using a γ table. Then, the image processing means for the final output, the measuring means for measuring the color reproduction characteristics of the image output by the image output means, the output value is predicted based on the memory map method, and the predicted value and the measuring means And a calibration means for interpolating the γ table so that the difference from the measured value is less than a predetermined value. 2. A color conversion method for executing color correction based on a memory map method using grid point data stored in advance, a first step of predicting an output value based on the memory map method, and calibration. A second step of measuring the output image by actually correcting the output data after color correction based on the memory map method, and the second step.
Calculating the sum of the differences between the measurement values measured by the step and the predicted value of the first step, and changing the γ table corresponding to each color so that the sum is less than or equal to a predetermined value,
And a third step of calibrating the γ table. 3. A color conversion method for executing color correction based on a memory map method using prestored grid point data, a first step of setting a reference value for ending calibration processing, and the memory map. A second step of predicting an output value based on the method, a third step of measuring the output image by actually outputting the calibration data after color correction based on the memory map method, and the third step. A γ table corresponding to each color is calculated such that the sum of the differences between the measurement values measured in the step and the predicted value in the second step is calculated and the sum is less than or equal to the reference value set in the first step. And a fourth step of calibrating the γ table. 4. A color conversion device for executing color correction based on a memory map method using previously stored grid point data, and a time measuring means for measuring the date and time when the calibration processing is executed, and a time measuring means for measuring the time. A color conversion device comprising: calibration data storage means for storing the date and time of calibration and its calibration data; and calibration means for performing calibration processing based on the calibration information stored in the calibration data storage means. . 5. A color conversion device for executing color correction based on a memory map method using grid point data stored in advance, and a monitoring means for monitoring a variation state of a portion contributing to color reproduction characteristics, and the monitoring means. A calibration notification means for determining whether or not calibration is necessary based on the monitoring information obtained by the means, and notifying that effect, and a display means for displaying the notification information sent from the calibration notification means. Color conversion device.